Polyamide Curing Agent Compositions

ABSTRACT

The present invention provides polyamide curing agent compositions comprising the reaction products of (1) multifunctional amines of structure 1 
     
       
         
         
             
             
         
       
     
     where R 1  is CH2CH2CH2NH2; R 2 , R 3  and R 4  independently are H or CH2CH2CH2NH2, and X is CH2CH2 or CH2CH2CH2 with (2) dimer fatty acids, optionally in combination with monofunctional fatty acids, the reaction product preferably comprising at least 15 wt % tetrahydropyrimidine-containing components. The curing agent compositions are useful for crosslinking epoxy resins to produce coatings, adhesives, floorings, composites and other articles.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of pending applicationSer. No. 11/450,834 filed 9 Jun. 2006.

BACKGROUND OF THE INVENTION

Polyamide curing agents are utilized extensively in many markets forepoxy curing agents including coatings, adhesives, composites, andflooring applications. Polyamide curing agents comprise the reactionproducts of dimerized fatty acid (dimer acid) and polyethyleneamines,and usually a certain amount of monomeric fatty acid which helps tocontrol molecular weight and viscosity. “Dimerized” or “dimer” or“polymerized” fatty acid refers, in a general way, to polymerized acidsobtained from unsaturated fatty acids. They are described more fully inT. E. Breuer, ‘Dimer Acids’, in J. I. Kroschwitz (ed.), Kirk-OthmerEncyclopedia of Chemical Technology, 4^(th) Ed., Wiley, New York, 1993,Vol. 8, pp. 223-237.

Dimer acid is usually prepared by the acid catalyzed oligomerizationunder pressure of certain monomeric unsaturated fatty acids, usuallytall oil fatty acid (TOFA), though sometimes other vegetable acids suchas soya fatty acid or cottonseed fatty acid are used. Commercialproducts generally consist of mostly (>70%) dimeric species, with therest consisting mostly of trimers and higher oligomers, along with smallamounts (generally less than 5%) of monomeric fatty acids. Commonmonofunctional unsaturated C16 to C22 fatty acids also employed with thedimer acids in making polyamides include tall oil fatty acid (TOFA),soya fatty acid, cottonseed fatty acid or the like.

Any of the higher polyethylene polyamines can be employed in thepreparation of polyamide curing agents, such as diethylenetriamine(DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA),pentaethylenehexamine (PEHA), hexaethyleneheptamine (HEHA), and thelike, though in actual commercial practice the polyethylene polyaminemost commonly employed is TETA.

In addition, other monofunctional or difunctional carboxylic acids, orother multifunctional amines may be incorporated into the condensationprocess in order to provide specialized property enhancements.

Polyethylene polyamines are currently manufactured from the reaction ofammonia with either ethylene dichloride or ethanolamine. As newmanufacturing assets are built to produce polyethylene polyamines, thereis a tendency to favor the ethanolamine process, as it is less corrosiveto the manufacturing equipment, and hence more economical.Unfortunately, the ethanolamine process generally produces less TETAthan the ethylene dichloride process, and therefore prices for TETA areincreasing relative to the prices for other polyethylene polyamines.There is therefore a need for more economical alternatives to TETA inthe manufacture of polyamide curing agents. However, it would beadvantageous if such an amine would have a molecular weight, aminehydrogen functionality, and chemical structure similar to TETA so as tominimize difficulties in re-formulation of end use products such ascoatings and adhesives.

U.S. Pat. No. 2,705,223 describes epoxy resins cured with polyamidesbased on polymeric fatty acids and polyethyleneamines.

GB 2,031,431 discloses epoxy resins cured with mixtures of highmolecular weight polyoxyalkylene polyamines andN,N′-bis(3-aminopropyl)ethylenediamine.

U.S. pat. No. 4,463,157 discloses self-curing amide-group-containingaminourea resins produced from a polyaminoamide which has been producedfrom polyalkylene-polyamines reacted with fatty acids and/or frompolyalkylene-polyamines reacted with dimer fatty acids. Table 1 of thispatent shows the product of reaction ofN,N′-bis(3-aminopropyl)ethylenediamine with ricinene fatty acid.

EP 134,970 describes similar polyaminoamides.

BRIEF SUMMARY OF THE INVENTION

The present invention provides polyamide curing agent compositionscomprising the reaction product of (1) an amine component comprising atleast one multifunctional amine of structure 1

where R₁ is CH2CH2CH2NH2; R₂, R₃ and R₄ independently are H orCH2CH2CH2N and X is CH2CH2 or CH2CH2CH2 with (2) a dimer fatty acid orester component, optionally, containing a monofunctional fatty acid.

In one aspect of the invention R₂ and R₃ are not H simultaneously.

In another aspect of the invention, the amine component that is reactedwith the dimer fatty acid or ester component comprises a mixture ofmono-, di-, tri- and tetra-substituted amines of structure 1 in a partsby weight (pbw) ratio of 0 to 50 pbw mono-substituted amine, 50 to 95pbw di-substituted amine and 0 to 50 pbw tri-substituted amine and 0 to25 pbw tetra-substituted amine, preferably a ratio of 0 to 20 pbwmono-substituted amine, 60 to 95 pbw di-substituted amine, 0 to 20 pbwtri-substituted amine and 0 to 10 pbw tetra-substituted amine.

In a further aspect of the invention the polyamide curing agentcomposition, i.e., the reaction product of the amine component and thedimer fatty acid component, comprises at least 15 mole %tetrahydropyrimidine-containing components.

As yet another aspect of the invention, there are provided epoxysystems, or compositions, comprising the contact product of the abovepolyamide curing agent, or curative, and an epoxy resin.

As an advantage of the current invention, the polyamide curing agentcompositions for epoxy resins often provide faster cure speed thanpolyamide curing agents of the current art. As another advantage of thecurrent invention, curing agent compositions are provided which do notcontain triethylenetetramine, but which have physical propertiesincluding viscosity, molecular weight and amine hydrogen equivalentweight that closely resemble polyamides derived fromtriethylenetetramine.

The curing agent compositions are useful for crosslinking epoxy resinsto produce coatings, adhesives, floorings, composites and otherarticles. Thus, another embodiment of the invention comprises coatings,adhesives, floorings, composites, and other cured epoxy articlesprepared by curing epoxy resins using such curing agents.

As yet another advantage, when the polyamide curing agent compositioncontains at least 15 mole % tetrahydropyrimidine-containing components,the curing agent composition affords 2-component polyamide coatingsmanifesting good coating appearance and fast dry speeds, in manyinstances dry through times of less than 24 hours.

DETAILED DESCRIPTION OF THE INVENTION

“Dimerized” or “dimer” or “polymerized” fatty acid refers, in a generalway, to polymerized acids obtained from unsaturated fatty acids. Theyare described more fully in T. E. Breuer, as noted above, whichdescription is incorporated by reference. Common monofunctionalunsaturated fatty acids used in making the dimer acid compositionsinclude tall oil fatty acid (TOFA), soya fatty acid and cottonseed fattyacid. The dimer acids are prepared by polymerizing the fatty acids underpressure, and then removing most of the unreacted fatty mono-acids bydistillation. The final product comprises mostly dimeric acids, butincludes trimeric as well as some higher acids. The ratio of dimericacids to trimeric and higher acids is variable, depending on processingconditions and the unsaturated acid feedstock. The dimer acid may alsobe further processed by, for example, hydrogenation, which reduces thedegree of unsaturation and the color of the product.

Suitable for the purposes of the present invention are dimer acids witha dimer content as measured by GC ranging from about 50 wt % to about 95wt %, and a trimer and higher acid content of from about 3 wt % to about40 wt %, the remainder being monomeric fatty acids. However, as theamount of trimer acid is increased, it will be necessary to increase theamount of polyamine and/or the amount of fatty mono-acid in order tomaintain the desired viscosity of the final product, since the higherfunctionality of the trimeric and higher fatty acids will lead to morebranching and increase the molecular weight in the product, and may evengel the product, as will be appreciated by those skilled in the art.Esters of dimer acids, particularly the C1 to C4 alkyl esters, can alsobe employed in the current invention.

Preferred dimer acid components are those with a range of dimeric acidsfrom 75 wt % to 90 wt %, including Empol® 1018 and Empol 1019® (CognisCorp.), Haridimer 250S (Harima M.I.D., Inc.), Yonglin YLD-70 (JiangsuYonglin Chemical Oil Co.), and Unidyme® 18 (Arizona Chemical Co.).

The fatty acids used in the current invention in combination with thedimer acids include C8 to C22, preferably C16 to C22 mono-carboxylicacids containing from 0 to about 4 units of unsaturation. Usually, suchfatty acids will be mixtures derived from triglycerides of naturalproducts, such as babassu, castor, coconut, corn, cottonseed, grapeseed,hempseed, kapok, linseed, wild mustard, oiticica, olive, ouri-curi,palm, palm kernel, peanut, perilla, poppyseed, rapeseed, safflower,sesame, soybean, sugarcane, sunflower, tall, teaseed, tung, uchuba, orwalnut oils. Pure fatty acids or mixtures of pure fatty acids, such asstearic, palmitic, oleic, linoleic, linolenic, etc. acids may also beemployed, as can various esters of any of these fatty acids,particularly the C1 to C4 esters. Also of utility is isostearic acid,also known as monomer acid. Monomer acid is the mostly C18 fattymono-acid stream derived from the preparation of dimer acid.

The preferred fatty acids to be blended with the dimer acids are talloil fatty acid and soya fatty acid.

If desired, other monofunctional and multifunctional carboxylic acidsmay be incorporated into the dimer acid portion of the reactioncomposition.

The multifunctional amines of structure 1 of the current inventioninclude N-3-aminopropyl ethylenediamine;N,N′-bis(3-aminopropyl)ethylenediamine;N,N-bis(3-aminopropyl)ethylenediamine;N,N,N′-tris(3-aminopropyl)ethylenediamine;N,N,N′,N′-tetrakis(3-aminopropyl)ethylenediamine; dipropylene triamine;N-3-aminopropyl-1,3-diaminopropane;N,N′-bis(3-aminopropyl)-1,3-diaminopropane;N,N-bis(3-aminopropyl)-1,3-diaminopropane; andN,N,N′-tris(3-aminopropyl)-1,3-diaminopropane;tetrakis(3-aminopropyl)-1,3-diaminopropane; and mixtures of theseamines. These multifunctional amines can be prepared by the Michaelreaction of either ethylene diamine or 1,3-diaminopropane withacrylonitrile, followed by hydrogenation over metal catalysts as is wellknown to those skilled in the art.

A preferred multifunctional amine for use as the amine component isN,N′-bis(3-aminopropyl)ethylenediamine. Most preferred as the aminecomponent is a mixture comprising 0-20 pbw of N-3-aminopropylethylenediamine, 60-95 pbw of N,N′-bis(3-aminopropyl)ethylenediamine,0-20 pbw of N,N,N′-tris(3-aminopropyl)ethylenediamine and 0-10 pbw ofN,N,N′,N′-tetrakis(3-aminopropyl)ethylenediamine. Such a mixture can beprepared by the reaction sequence described above for making themultifunctional amine without the need to conduct a distillation orother process of separation, except for the optional removal of lowmolecular weight side products of the reaction which are more volatilethan N-3-aminopropyl ethylenediamine. It will be recognized by thoseskilled in the art that small quantities of other products ofhydrogenation may be present in the mixture.

If desired, the curing agent composition may be modified byincorporation of other multifunctional amines. Examples includeethylenediamine, diethylenetriamine, triethylenetetramine,tetraethylenepentamine, higher polyethyleneamines, aminoethylpiperazine,meta-xylylene diamine, the various isomers of diamine-cyclohexane,isophorone diamine, 3,3′-dimethyl-4,4′-diaminodicyclohexyl methane,4,4′-diaminodicyclohexyl methane, 2,4′-diaminodicyclohexyl methane, themixture of methylene bridged poly(cyclohexyl-aromatic)amines (MBPCAA)described in U.S. Pat. No. 5,280,091, 1,2-propylene diamine,1,3-propylene diamine, 1,4-butanediamine, 1,5-pentanediamine,1,3-pentanediamine, 1,6-hexanediamine,3,3,5-trimethyl-1,6-hexane-diamine, 3,5,5-trimethyl-1,6-hexanediamine,2-methyl-1,5-pentanediamine, bis-(3-amino-propyl)amine,N,N′-bis-(3-aminopropyl)-1,2-ethanediamine,N-(3-aminopropyl)-1,2-ethanediamine, 1,2-diaminocyclohexane,1,3-diaminocyclohexane, 1,4-diamino-cyclohexane, the poly(alkyleneoxide)diamines and triamines (such as for example Jeffamine D-230,Jeffamine D-400, Jeffamine D-2000, Jeffamine D-4000, Jeffamine T-403,Jeffamine EDR-148, Jeffamine EDR-192, Jeffamine C-346, Jeffamine ED-600,Jeffamine ED-900, Jeffamine ED-2001 and also aminopropylated ethyleneglycols, propanediols, butanediols, hexanediols, polyethylene glycols,polypropylene glycols and polybutanediols. The polyamide curativecomposition can either be modified by incorporating these polyamines inthe condensation reaction with the dimer acid, or by adding them to thepolyamide after completion of the condensation reaction. In the formercase, it is then necessary to adjust the ratio of moles of polyamine toequivalents of acid to conform with the guidelines given below.

The percentage of equivalents of fatty mono-acids to total equivalentsof monofunctional plus multifunctional acids can be varied from 0 toabout 30%, preferably from 3% to 20. The equivalents of acid can beobtained by titration of the starting materials with alcoholichydroxide, as is well known in the art. Those skilled in the art willrecognize that increasing the percentage of monofunctional acid willlower the molecular weight and viscosity of the polyamide. They willalso recognize that increasing the trimer and higher acid content of thedimer acid will increase the molecular weight and viscosity of thepolyamide.

The ratio of total moles of multifunctional amine to equivalents ofacid, along with the functionality of the multifunctional amine, arecrucial parameters in determining the molecular weight, viscosity, andother properties of the resulting polyamides. Indeed, if the ratio ofamine to acid is not large enough, then the entire composition can gel.Furthermore, this ratio also influences the amine hydrogen equivalentweight (AHEW) of the final product, and has an effect upon the amount ofunreacted multifunctional amine present after completion of thecondensation reaction. Unreacted multifunctional amine can causedeleterious effects to surface appearance and intercoat adhesion.Suitable ratios of moles of multifunctional amine to equivalents of acidrange from about 0.4:1 to about 1.2:1, preferably from 0.5:1 to 1:1. Themoles of amine is calculated from the number average molecular weight,if a mixture of amines is employed.

Polyamides of the current invention can be manufactured by any number ofprocesses known to those skilled in the art. Normally, the amines andacids are combined at temperatures ranging from about room temperatureto about 100° C. Heat is then supplied to raise the temperature as wateris condensed from the reaction mixture. Heating is normally continueduntil the specified amount of water is removed that will yield a productwith the desired amide and imidazoline or tetrahydropyrimidine content.Optionally, vacuum can be applied particularly in the late stages of theprocess to aid in the removal of water from the mixture. To reducefoaming, which can be a problem particularly under vacuum conditions,small amounts of defoamers may be added to the polyamide composition.Appropriate defoamers include various acrylic copolymers containing2-ethylhexyl acrylate as part of the copolymer composition, variouspolysiloxane copolymers, and the like.

During the condensation reaction, it is possible to cause some of theamine functional amides to cyclize with further loss of water to formtetrahydropyrimidines, as shown below for tetrahydropyrimidines. Drivingthe reaction to form higher levels of tetrahydropyrimidines mayinfluence the properties of the polyamide curing agent, such as, forinstance, improving cure speed and improving the appearance of thecoating. All possible levels of tetrahydropyrimidine functionality ofthe polyamide curing agents are considered to be part of the currentinvention. However, in one desirable aspect the polyamide curing agentcomposition comprises at least 15 mole % tetrahydropyrimidine-containingcomponents, preferably at least 20 mole % and especially at least 25mole % tetrahydropyrimidine-containing components, as determined by 13CNMR. In some aspects an upper limit for thetetrahydropyrimidine-containing components would be 75 mole %.

The polyamide curing agent, or hardener, is combined with an epoxy resinwhich is a polyepoxy compound containing about 2 or more 1,2-epoxygroups per molecule. Such epoxides are described in Y. Tanaka,“Synthesis and Characteristics of Epoxides”, in C. A. May, ed., EpoxyResins Chemistry and Technology (Marcel Dekker, 1988), and areincorporated by reference. Such combination of polyamide curing agentand epoxy resin composes a curable epoxy system.

The preferred polyepoxy compounds are the diglycidyl ethers ofbisphenol-A, the advanced diglycidyl ethers of bisphenol-A, thediglycidyl ethers of bisphenol-F, and the epoxy novolac resins.

To reduce the viscosity of a given formulation of polyamides of thecurrent invention with a di- or multi-functional epoxy resin, the epoxyresin may be modified with a portion of monofunctional epoxide. In thisway viscosity is further reduced, which may be advantageous in certaincases, such as for example to increase the level of pigment in aformulation while still allowing easy application, or to allow the useof a higher molecular weight epoxy resin. Examples of usefulmonoepoxides include styrene oxide, cyclohexene oxide, ethylene oxide,propylene oxide, butylene oxide, and the glycidyl ethers of phenol, thecresols, tert-butylphenol and other alkyl phenols, butanol,2-ethyl-hexanol, and C8 to C14 alcohols and the like.

Polyamides of the current invention would normally be formulated withepoxy resins at stoichiometric ratios of epoxy groups to amine hydrogenranging from about 1.5 to 1 to about 1 to 1.5. More preferred are rangesfrom 1.2 to 1 to 1 to 1.2.

It is also possible to modify the polyamides of the current invention byreacting a modest portion of the amine hydrogen with difunctional andmonofunctional epoxy resins such as those described above. This is acommon practice well known to those skilled in the art, and generallyreferred to as “adduction”. By adducting with difunctional andmonofunctional epoxy resins it is possible to improve the compatibilityof the polyamide with epoxy resin and thereby reduce problems such asblush, carbonation and exudation as described above, and to increase potlife. On the other hand, such modification tends to increase viscosity,particularly in the case of difunctional epoxy resins, and may in somecases also decrease the rate of cure. Particularly useful epoxy resinsfor adduction include the diglycidyl ethers of bisphenol-A, the advanceddiglycidyl ethers of bisphenol-A, the diglycidyl ethers of andbisphenol-F, styrene oxide, cyclohexene oxide, and the glycidyl ethersof phenol, the cresols, tert-butylphenol and other alkyl phenols,butanol, 2-ethylhexanol, and C8 to C14 alcohols and the like. It is alsopossible to accomplish a modest level of adduction by mixing the amineand epoxy components and allowing them to stand for some period of timeknown as an induction period to those skilled in the art, normally 15 to60 minutes, before application.

In some circumstances it may be advantageous to incorporate so-calledaccelerators for the epoxy-amine curing reaction in formulations basedon polyamides of the current invention. Such accelerators are describedin H. Lee and K. Neville, Handbook of Epoxy Resins, McGraw-Hill, NewYork, 1967. Suitable accelerators include various organic acids,alcohols, phenols, tertiary amines, hydroxylamines, and the like.Particularly useful accelerators include benzyl alcohol, phenol, alkylsubstituted phenols such as nonylphenol, octylphenol, t-butylphenol,cresol and the like, bisphenol-A, salicylic acid,dimethylaminomethylphenol, bis(dimethylaminomethyl)phenol, andtris(dimethylaminomethyl)phenol. Normally, such accelerators are used atlevels of 10% or less based on the total weight of binder, and moreusually at levels of less than 5%.

In some circumstances it may be advantageous to incorporate plasticizersfor the epoxy-amine network in formulations based on polyamides of thecurrent invention. This is particularly useful in cases where, in theabsence of such a plasticizer, the glass transition temperature, Tg, ofthe composition significantly exceeds the ambient temperature before thedegree of reaction necessary to meet certain requirements such assolvent and chemical resistance and tensile strength has been achieved.Such plasticizers are well known to those skilled in the art, and aredescribed more fully in D. F. Cadogan and C. J. Howick, ‘Plasticizers’,in J. I. Kroschwitz, ed., Kirk-Othmer Encyclopedia of ChemicalTechnology, 4^(th) Ed., Wiley, New York, 1996, Vol. 19, pp. 258-290.Particularly useful plasticizers include benzyl alcohol, nonylphenol,and various esters of phthalic acid. The ester plasticizers wouldnormally be incorporated in the same package as the epoxy resin tominimize reaction with the amine curing agent. Another particularlyuseful class of plasticizers are hydrocarbon resins, which includetoluene-formaldhyde condensates such as Epodil® L, xylene-formaldehydecondensates such as Nikanol® Y50, coumarone-indene resins, and manyother hydrocarbon resin modifiers well know to those skilled in the art.

Coatings prepared from polyamides of the current invention and epoxyresins can be formulated with a wide variety of ingredients well knownto those skilled in the art of coating formulation, including solvents,fillers, pigments, pigment dispersing agents, rheology modifiers,thixotropes, flow and leveling aids, defoamers, etc. Mixtures ofsolvents will frequently be chosen so as to give the best evaporationrate profile for the system while maintaining solubility of the bindercomponents. Suitable solvents include aromatics, aliphatics, esters,ketones, ethers, alcohols, glycols, glycol ethers, and the like.Particularly useful in the formulation are some level of ketones such asacetone, methyl ethyl ketone, methyl isoamyl ketone, methyl propylketone, methyl amyl ketone, diacetone alcohol and the like, which can beused to improve pot life with little or no sacrifice in dry speed. Ifester solvents are included in the formulation, it is usually necessaryto formulate them in the package containing the epoxy resin, so as tominimize their reaction with the amine curing agent. Sometimes the epoxyresins used in the practice of this invention will be supplied insolvent cut versions, and likewise, it may be of value to use thepolyamides of the current invention, or other curing agents used incombination with these polyamides, as solvent-cut versions.

Coatings of this invention can be applied by any number of techniquesincluding spray, brush, roller, paint mitt, and the like. Numeroussubstrates are suitable for application of coatings of this inventionwith proper surface preparation, as is well understood in the art. Suchsubstrates include but are not limited to many types of metal,particularly steel and aluminum, as well as concrete.

Coatings of this invention can be applied and cured at ambienttemperatures ranging from about 0° C. to about 50° C., with temperaturesof 10° C. to 40° C. preferred. If desired, these coatings can also beforce cured at temperatures up to 150° C. or more.

EXAMPLE 1 Synthesis of 3-aminopropyl-1,3-diaminopropane

To a batch reactor was added 510.4 g of acrylonitrile and 6 g of water.The contents were heated to 60° C. To this mixture was added 85 g ofammonia over 5 hours. The reactor pressure was maintained at 2.4 MPa tokeep the ammonia liquid. Once the ammonia addition was completed thereactor temperature was maintained for an additional two hours. Thereactor was then cooled and the contents were emptied to yield 572.5 gof the intermediate product.

A 1 liter batch reactor was charged with 100 g of isopropanol and 3.9 gof Raney Co catalyst. The reactor was pressure cycled first withnitrogen and then with hydrogen to remove any traces of entrained air.After pressure cycling, the reactor was filled with 5.5 MPa hydrogen andheated to 120° C. Then 260 g of product from the previous step was addedto the reactor over 4 hours. During this time reactor pressure wasmaintained at 5.5 MPa by supplying hydrogen to it from a one literballast tank. Once the addition was over the temperature was maintainedat 120° C. for an additional hour to make sure the hydrogenation wascomplete.

The reactor was cooled down to room temperature, and the product wasfiltered. The product was analyzed by area percent GC and it contained74% 3-aminopropyl-1,3-diaminopropane and 14% 1,3-diaminopropane.

EXAMPLE 2 Synthesis of Polyamide from Example 1

To a one liter glass reactor, 380.6 g of dimer acid (Pripol 1012,Uniqema) was added while purging the system slowly with nitrogen. Thestirrer was started after the addition of dimer acid and 47.3 g of TOFA(Sylfat FA-1, Arizona Chemical Co.) was added slowly to this system.Next 110.4 g of the product from Example 1 was added over ten minutesand the stirrer rate was increased to 100 rpm. The contents were thenheated to 250° C. and 36.5 g of water was removed by distillation. Thereactor was cooled down to 140° C. and at this point 263.3 g of xylenewas added and the reactor was further cooled to less than 80° C. andfinally 122.5 g of isobutyl alcohol was added. The final product wasgolden-brown in color. The product had an AHEW of 502.

EXAMPLE 3 Synthesis of Mixture of N-3-aminopropyl ethylenediamine,N,N′-bis(3-aminopropyl)ethylenediamine, andN,N,N′-tris(3-aminopropyl)ethylenediamine

To a 1 liter batch reactor was added 236 g of ethylenediamine and tothat 5 g of water was added, and the contents were heated to 60° C. Tothis mixture 417 g of acrylonitrile was added over 5 hours. Once theacrylonitrile addition was completed the reactor temperature wasmaintained for an additional 1.5 hours.

A 1 liter batch reactor was charged with 100 g of isopropanol, 6.6 g ofwater and 7.5 g of Raney Co catalyst. The reactor was pressure cycledfirst with nitrogen and then with hydrogen to remove any traces ofentrained air. After pressure cycling, the reactor was filled with 5.5MPa hydrogen and then heated to 120° C. The 500 g of product from theprevious step was the added to the reactor over 4 hours. During thistime reactor pressure was maintained at 5.5 MPa by supplying hydrogen toit from a one liter ballast tank. Once the addition was over thetemperature was maintained at 120° C. for an additional hour to makesure the hydrogenation was complete.

The reactor was cooled down to room temperature, and the product wasfiltered. The product was analyzed by area percent GC and it contained6% N-3-aminopropyl ethylenediamine, 80%N,N′-bis(3-aminopropyl)ethylenediamine, and 11%N,N,N′-tris(3-aminopropyl)ethylenediamine and 2%N,N.N′,N′-tetrakis(3-aminopropyl)ethylenediamine.

EXAMPLE 4 Synthesis of Polyamide from Example 3

To a one liter glass reactor, 445.0 g of dimer acid (Yonglin YLD-70) wasadded while purging the system slowly with nitrogen. The stirrer wasstarted after the addition of the dimer acid and 51.0 g of TOFA (SylfatFA-1 was added slowly to this system. Next 299.4 g of the Example 3product was added over ten minutes and the stirrer rate was increased to100 rpm. The contents were then heated to 265° C. and 56.0 g of waterwas removed by distillation. The reactor was cooled to 65° C. and thecontents were emptied to a glass bottle. The final product had an aminevalue of 361 mg KOH/g, a viscosity of 30,000 mPa·s, a Gardner color of 8and a calculated amine hydrogen equivalent weight (AHEW) of 110.

EXAMPLE 5 Synthesis of Polyamide from a Mixture of Example 3 andEthylenediamine

To a one liter glass reactor, 234.9 g of Empol 1018 dimer acid (Cognis)was added while purging the system slowly with nitrogen. The stirrer wasstarted and 26.7 g of TOFA (Sylfat FA-2) was added slowly. Next wasadded 124.8 g of the amine mixture of Example 3 and 15.6 g ofethylenediamine over ten minutes and the stirrer rate was increased to100 rpm. The contents were then heated to 265° C. and 27.6 g of waterwas removed by distillation. The reactor was cooled to 65° C. and thecontents were emptied to a glass bottle. The final product had an aminevalue of 341 mg KOH/g and a viscosity of 36,640 mPa·s.

EXAMPLE 6 Synthesis of Higher Molecular Weight Polyamide from Example 3

To a reactor was added 232 g of Example 3, 106 g of TOFA (Sylfat FA-2)and 572 g of Empol 1018 dimer acid (Cognis). The mixture was heated to160° C., and which point water began to distill. Over 2 hr., the mixturewas heated to 215° C., at which point the pressure was reduced to 150torr. The temperature was raised to 230° C. over 30 min. The temperaturewas held until 53.0 g of water had been removed, at which point thecontents were cooled. The final product had an amine value of 150 mgKOH/g and a viscosity of 473,600 mPa·s.

EXAMPLES 7-9 Coating Formulations and Properties

A pigmented resin base was prepared in a standard manner by charging98.8 g of DER® 331 epoxy resin (Dow Chemical Co., EEW=190) and 3.5 gNuosperse® 657 (Elementis pic) to a dispersion vessel. The vessel wasequipped with a high speed mixer employing a Cowles blade. To this 100.8g TiPure® R900 titanium dioxide (E. I. DuPont de Nemours Co.) and 74.8 gof Luzenac® 10M2 (Luzenac Group) were added under high shear (approx.4000 rpm) over a 5-10 minute period with a further period of 20-30minutes dispersion before dilution of this with 71.7 g xylene and 17.9 gbutanol followed by further blending for about 5 minutes at lower shear(1000 rpm). This formulated resin base has a viscosity of 200-300 mPa·sand an epoxy equivalent weight of approx. 710.

The resin base was combined with the curing agents indicated infollowing Table 1 by hand mixing. After mixing and an induction time of15 minutes coatings were applied to glass panels at 175 microns wet filmthickness using a bird-bar applicator. The coated glass panels wereevaluated for:

-   -   a) Thin Film Set Time using a Beck Koller drying time recorder        at a constant temperature of 23° C. and 60% relative humidity.        Phase II and Phase III drying times were assigned according to        ASTM D5895.    -   b) Persoz pendulum hardness using a BYK pendulum hardness tester        to ISO 1522 standard.    -   c) Specular gloss was measured using a BYK Micro Tri Gloss model        No. 4520 to ISO 2813 standard.

All results are shown in Table 1.

TABLE 1 Example 7 8 9 Polyamide Curing Agent Ancamide ® Example 4Example 5 350A Formulation Curing Agent Wt. (g) 6.0 6.0 6.0 Resin BaseWt. (g) 37.2 37.2 37.2 PVC % 25 25 25 Mix Solids (wt & vol %) 78 & 65 78& 65 78 & 65 Handling Mix Viscosity @ 23° C. Properties (mPa · s)  0minutes 455 415 390 30 minutes 610 690 640 Coating Thin Film Set @ 23°C. Performance BK - Phase II (hr.) 6.5 3.0 3.5 BK - Phase III (hr.) 8.03.5 4.0 Persoz Hardness @ 23° C. 1 day 40 70 85 2 day 110 105 115 7 day155 140 155 Specular Gloss 20°/60° 24/70 25/73 10/45

Ancamide® 350A curative is a polyamide curing agent based on dimer acid,TOFA and TETA which is available from Air Products and Chemicals, Inc.,with a viscosity of 15,000 mPa·s, a Gardner color of 7, an amine valueof 360 to 390 mg KOH/g, and an AHEW of 110.

The Thin Film Set Times at 23° C. of coatings derived from the currentinvention (Examples 8 and 9) are significantly faster than Example 7;with the times taken to reach Phase II and Phase III approximately halfof the standard TETA based polyamide (Ancamide® 350A). This is anindication that the current invention exhibits earlier hardnessdevelopment which may lead to the ability to handle coated componentssooner and overcoat quicker, providing the opportunity to increaseproductivity within the coatings application. The early hardnessdevelopment is also shown by the one day hardness being significantlyhigher for Examples 8 and 9 compared to Example 7, with 7 day hardnessbeing comparable. The Example 4 curing agent, however, had an AHEW andamine value within the specified range of the comparative commerciallyavailable TETA based polyamide. Though the viscosity of the polyamide ofExample 4 was higher than that of the comparative hardener, itsurprisingly led to a mixed viscosity that was slightly lower. It is themix viscosity that determines the applicability of the product, andtherefore the ultimate solvent content or VOC of the coating, indicatinganother advantage of the polyamides of the current invention over thoseof the current art.

EXAMPLE 10

Dimer acid (Uniquema Pripol 1017) 576 g,N,N′-bis-(3-aminopropyl)ethylenediamine composition (Example 3 reactionproduct) 366 g and TOFA (Sylfat FA-2) 70 g were mixed together and thenheated to 166° C. At 166° C., 18 g of water was removed using adistillation column. When there was no further water in the column, thereactor temperature was increased to 214° C. and a further 10 g of waterwas removed making the total water take off 28 g. Also, 300 g of thereaction product (Sample 1) was removed for analytical work. Once therewas no water remaining in the column, the temperature was raised to 232°C., and the reactor pressure lowered to 150 mm Hg. Under theseconditions an additional 10 g of water was removed and collected in thereceiver, resulting in a total water take off 38 g. At this pointanother 100 g of polyamide material was sampled for analysis (Sample 2).Finally, the reactor was heated to 240° C., and the pressure lowered to25 mm Hg. Under these conditions an additional 11 g of water (49 gramstotal) was removed and a final sample of the polyamide was taken (Sample3). Samples 1, 2 and 3 were subjected to 13C NMR analysis to determinethe polyamide and the pyrimidine content.

Each sample of the polyamide reaction product was mixed with Epon 828resin (Bisphenol A diglycidyl ether resin; 190 EEW) at 55 parts byweight per hundred parts Epon 828 resin (phr) until a homogeneousmixture was obtained and after a 30 min aging period the mixtures werecast onto a BK recorder glass plate using a die applicator at 150microns to make a epoxy-polyamide film. The scale of the BK recorder wasset at 24 hrs. The observations for dry-hard and dry-through values wererecorded according to the ASTM method for drying times (ASTM D 5895-96).

The analytical results of the respective properties are shown below.

Sample # 1 2 3 Polyamide Product Composition Polyamide - amide content100 87 76 (mole %) Tetrahydropyrimidine content 0 13 24 by NMR (mole %)Coating Performance Dry-Hard (hr) 10 8 6.5 Dry-Through (hr) >24 >24 12.5Appearance opaque opaque good

As shown in the results above, it is clear that 2-componentepoxy-polyamide films, or coatings, that contain zero to low levels ofthe pyrimidine ring structure did not give desirable coating properties,such as the appearance, hard dry and dry-through times. It is veryimportant in the coatings industry for 2 component polyamide coatings todemonstrate good coating appearance and fast dry speeds at ambienttemperature for improved return to service of the article that hasundergone painting. Therefore, to have epoxy systems with ultimate drythrough times <24 hr is a recognized performance benefit in theindustry. The results clearly show that for desirable properties,polyamide curing agent compositions with greater than about 15 mole %pyrimidine structure content are necessary, as determined by 13C NMR.

Thus, another feature of an aspect of the invention is that the curingagent composition manifests a dry through time of less than 24 hoursaccording ASTM D 5895-96 when mixed with liquid Bisphenol A diglycidylether epoxy resin (Epon 828 or Dow DER 331) having an EEW of 190 at 55phr until homogenous, allowed to mature for 30 minutes and coated at 150microns.

1. A polyamide curative composition comprising a reaction product of (1)an amine component comprising at least one multifunctional amine ofstructure 1

where R₁ is CH2CH2CH2NH2; R₂, R₃ and R₄ independently are H orCH2CH2CH2NH2; and X is CH2CH2 or CH2CH2CH2 with (2) a dimer fatty acidor ester component, optionally, containing a monofunctional fatty acid,the reaction product comprising at least 15 mole %tetrahydropyrimidine-containing components.
 2. The curative compositionof claim 1 in which the amine component comprises a mixture of mono-,di-, tri- and tetra-substituted amines of structure 1 in parts by weight(pbw) of 0-20 pbw mono-substituted amine, 60-95 pbw di-substitutedamine, 0-20 pbw tri-substituted amine, and 0-10% tetra-substitutedamine.
 3. The curative composition of claim 2 in which the amine mixturecomprises N-3-aminopropyl ethylenediamine,N,N′-bis(3-aminopropyl)ethylenediamine,N,N,N′-tris(3-aminopropyl)ethylenediamine andN,N,N′N′-tetrakis(3-aminopropyl)ethylenediamine.
 4. The curativecomposition of claim 1 in which the dimer component also comprises amonofunctional fatty acid.
 5. The curative composition of claim 1 inwhich the dimer acid component has a dimer acid content ranging fromabout 50 wt % to about 95 wt %, and a trimer and higher acid content offrom about 3 wt % to about 40 wt %, the remainder being monomeric fattyacid.
 6. The curative composition of claim 5 in which the dimer acid isprepared from tall oil fatty acid, soya fatty acid or cottonseed fattyacid.
 7. The curative composition of claim 4 in which the monofunctionalfatty acid is a C16-C22 monocarboxylic acid having from 0 to 4 units ofunsaturation.
 8. The curative composition of claim 1 in which the aminecomponent comprises N,N′-bis(3-aminopropyl)ethylenediamine.
 9. Thecurative composition of claim 7 in which the percentage of equivalentsof fatty mono-acids to total equivalents of monofunctional plusmultifunctional acids is from 0 to about 30%.
 10. The curativecomposition of claim 1 in which a portion of the amine hydrogens of thepolyamide are reacted with a difunctional or monofunctional epoxy resin,or both.
 11. A polyamide curative composition comprising a reactionproduct of (1) an amine component comprising at least onemultifunctional amine of structure 1

where R₁ is CH2CH2CH2NH2; R₂, R₃ and R₄ independently are H orCH2CH2CH2NH2; and X is CH2CH2 or CH2CH2CH2 with (2) a dimer fatty acidcomponent, optionally containing a monofunctional fatty acid, the aminecomponent (1) comprising a mixture of mono-, di-, tri- andtetra-substituted amines of structure 1 in parts by weight (pbw) of 0-20pbw mono-substituted amine, 60-95 pbw di-substituted amine, 0-20 pbwtri-substituted amine and 0-10 parts tetra-substituted amine, the aminecomponent (1) and dimer component (2) reacted in a ratio of moles ofmultifunctional amine to equivalents of acid from about 0.4:1 to about1.2:1, the reaction product further comprising at least 15 mole %tetrahydropyrimidine-containing components.
 12. The curative compositionof claim 11 in which X is CH2CH2.
 13. The curative composition of claim12 in which the amine mixture comprises N-3-aminopropyl ethylenediamine,N,N′-bis(3-aminopropyl)ethylenediamine,N,N,N′-tris(3-aminopropyl)ethylenediamine andN,N,N′N′-tetrakis(3-aminopropyl)ethylenediamine.
 14. The curativecomposition of claim 13 in which the dimer component also comprises amonofunctional fatty acid.
 15. The curative composition of claim 13 inwhich the dimer acid component has a dimer acid content ranging fromabout 50 wt % to about 95 wt %, and a trimer and higher acid content offrom about 3 wt % to about 40 wt %, the remainder being monomeric fattyacid.
 16. The curative composition of claim 15 in which the dimer acidis prepared from tall oil fatty acid, soya fatty acid or cottonseedfatty acid.
 17. The curative composition of claim 16 in which themonofunctional fatty acid is a C16-C22 monocarboxylic acid having from 0to 4 units of unsaturation.
 18. The curative composition of claim 17 inwhich the amine component comprisesN,N′-bis(3-aminopropyl)ethylenediamine.
 19. The curative composition ofclaim 17 in which the percentage of equivalents of fatty mono-acids tototal equivalents of monofunctional plus multifunctional acids is from 0to about 30%.
 20. The curative composition of claim 17 in which aportion of the amine hydrogens of the polyamide are reacted with adifunctional or monofunctional epoxy resin, or both.
 21. An epoxycomposition comprising the contact product of a polyamine curativecomposition of claim 1 and an epoxy resin in a stoichiometric ratio ofepoxy groups to amine hydrogens ranging from about 1.5:1 to about 1:1.5.22. The epoxy composition of claim 21 in which the epoxy resin is adiglycidyl ether of bisphenol-A, an advanced diglycidyl ether ofbisphenol-A, a diglycidyl ether of bisphenol-F, an epoxy novolac resin,or a mixture thereof.
 23. A polyamide curative composition comprising areaction product of (1) an amine component comprisingN,N′-bis(3-aminopropyl)ethylenediamine with (2) a dimer fatty acidcomponent which is prepared from tall oil fatty acid, soya fatty acid orcottonseed fatty acid, optionally, containing a C16-C22 monocarboxylicacid having from 0 to 4 units of unsaturation, the reaction productcomprising at least 15 mole % tetrahydropyrimidine-containingcomponents.
 24. The curative composition of claim 23 which manifests adry through time of less than 24 hours according ASTM D 5895-96 whenmixed with liquid Bisphenol A diglycidyl ether epoxy resin having an EEWof 190 at 55 phr until homogenous, allowed to mature for 30 minutes andcoated at 150 microns.